Type I diabetes, or IDDM, is an autoimmune disease caused by T cells that attack and destroy the insulin-producing cells located in the islets of the pancreas (23). The autoimmune process culminating in IDDM begins and progresses without symptoms. The disease surfaces clinically only when the cumulative loss of .beta.-cells exceeds the capacity of the residual .beta.-cells to supply insulin. Indeed, the collapse of glucose homeostasis and clinical IDDM is thought to occur only after 80-90% of the .beta.-cells have been inactivated by the immune system. Thus, patients who can be identified as suffering from IDDM are bound to be in an advanced stage of autoimmune destruction of their .beta.-cells. Moreover, diagnosis of incipient, pre-clinical diabetes by the detection of immunological markers of .beta.-cell autoimmunity can be made only after the onset of the autoimmune process. Therefore, the therapeutic quest is to find a safe, specific and effective way to turn off an autoimmune process that is already well underway.
The present inventors have examined this question before by studying the spontaneous diabetes developing in mice of the NOD strain, which is considered to be a faithful model of human IDDM (23-25). NOD mice develop insulitis around one month of age, which begins as a mild peri-islet infiltrate and progresses to severe intra-islet inflammation. Hyperglycemia, which attests to insulin insufficiency, begins in the females in our colony at about three months of age. By six months of age, almost all the female NOD mice have developed severe diabetes and most die in the absence of insulin treatment. Male NOD mice have a lower incidence of disease, for reasons that are not clear. The diabetes of NOD mice has been shown to be caused by autoimmune T cells (26).
T cell reactivity and auto-antibodies to various antigens have been detected in human IDDM patients as well as in NOD mice (27), and it is not clear whether immunity to any single one of the possible target antigens is the primary cause of the disease. Beyond the question of causation is the question of therapy.
It has been demonstrated that the initiation of the autoimmune process in NOD mice can be prevented by subjecting the mice, before the onset of diabetes, to various manipulations such as restricted diet, viral infections, or non-specific stimulation of the immune system (24). NOD diabetes is also preventable by induction of immunological tolerance in pre-diabetic mice to the antigen glutamic acid decarboxylase (GAD) (28, 29).
Anti-idiotypic T cells are T cells that recognize peptides derived from the antigen receptors of other T cells (6). It is thought that anti-idiotypic T cells are involved in regulating the activities of the T cells whose T cell receptor (TCR) peptides they recognize. Autoimmune T cells might be subject to regulation by anti-idiotypic T cells: anti-idiotypic T cells have been detected following intentional T cell vaccination of rodents in the model of experimental autoimmune encephalomyelitis (EAE) (6) or of humans (7) suffering from multiple sclerosis (MS) with autoimmune T cells.
European patent application 261,648 discloses the use of activated T cells specific for an autoimmune disease for the treatment of such disease. The T cells are preferably first pressure treated, subjected to a chemical cross-linking agent and/or subjected to a cytoskeletal disrupting agent in order to improve their immunogenicity. The entire treated cell or fraction thereof may be used as a vaccine against the autoimmune disease for which the T cell is specific.
In the known procedure for causing the arrest of autoimmune T cells, the subject is immunized with a sample of attenuated or avirulent T cells of the particular autoimmune specificity, or fragments or fractions thereof. The subject responds by activating regulatory T cells of at least two types: anti-ergotypic T cells that recognize T cell activation markers and anti-idiotypic T cells that appear to recognize the self-antigen receptors present on the pathogenic endogenous autoimmune T cells. T cell vaccination in experimental animals is effective in inducing permanent remission of established disease as well as in preventing disease. Use of peptide sequences of a T cell receptor .beta. chain has been disclosed for vaccination of rats against experimental autoimmune encephalomyelitis (30, 31), thereby supporting the conclusion that the autoimmtme T cell receptor itself can supply a target epitope for regulator T cells.
In the present invention, it is shown that the spontaneous development of diabetes in NOD mice is regulated by an anti-regulated network in which the anti-idiotypic T cells are specific for a TCR VDJ peptide of an autoimmune T cell commonly expressed in mice of the non-obese diabetic (NOD) strain (1).
Functional Role of hsp60 and p277 Peptide in IDDM
The laboratory of the present inventors has previously demonstrated that an epitope of the 60 KDa heat shock protein (hsp60) is a target of autoimmune attack in the type I diabetes mellitus that develops spontaneously in the NOD strain of mice (2). This protein was formerly designated hsp65, but is now designated hsp60 in view of more accurate molecular weight information; by either designation, the proteins are the same. This laboratory has previously identified a peptide fragment from the human hspGo sequence, designated peptide p277 (SEQ ID NO:5), that contains a target epitope for T cells mediating diabetes (3; PCT publication WO 90/10449).
This laboratory has also isolated a clone of T cells, designated clone C9, that recognizes peptide p277 and can produce diabetes (3). Both the p277 peptide and the C9 T cells were found to have a functional role in controlling diabetes: vaccination of NOD mice with either attenuated C9 T cells or with peptide p277 could prevent (3) or even reverse diabetes (4). Both of these therapeutic vaccinations activate the anti-idiotypic regulator T cells.